Impulse amplifier



May 8, 1 945.

SOURCE O F IMPULSE S c. E. HALLMARK 2,375,551

IMPULSE AMPLIFIER Filed March 18, 1943 CONTROLLED I8 APPARATUS INVENTORHALLMARK Patented May 8, 1945 UNITED STATES PATENT OFFICE IMP LSEAMPLIFIER Clyde E. Hallmark, Fort Wayne, Ind., assignor to FarnworthTelevision and Radio Corporation, a corporation of Delaware 7Application March 1a, 1943, Serial No. 479,567

, a 6 Claims. (01. 178-75) This invention relates to electronicamplifiers and particularly to apparatusadapted to amplifyunidirectional impulses such as those employed in television systems.

' According to conventional practice in television systems,unidirectional impulses are used fora number of diflerent purposes.Typical uses for the receiver the synchronizing impulses must beseparated from-thevideo signals of a composite television signalincludingboth types of signals. Frequently the separating and amplifyingfunctions are performed by the same apparatus.

' As is well understood in the art, however, where I a relatively highoverall amplification of the ,im-

pulses .is'required, several amplifying stages may be needed. When highlevel positive output pulses are required the efliciency of suchapparatus from a power consumption standpoint is quite low.

An object vof the presentinvention' therefore,

is to. provide a novel multi-stage amplifier which is capable of a largeoutput and which has a high overall power efliciency. i

Another object of the invention is to provide novel means for separatingthe synchronizing impulsesfrom the video signal portion of acompositetelevision signal.

A'further object of the inventionis to provide a sourceofpolarizingpotential to be applied to the anode circuit of a driving stage andderivable from an electrode of the driven stage.

In accordance with the present invention, there is provided amulti-stage amplifier, Each amplisynchronizing impulses is impressedupon the infier stage includes an electronic device having an input andan output circuit. Theimpulses to be amplified are impressed upon theinput circuit of the first amplifier stage and the amplified impulsesare derived from a load impedance included in the output circuit of asucceeding stage.

There is provided as part of the load impedance, an integrating circuitwhich is adapted to translate the impulsive energy applied theretofrom'the output circuit of the succeeding stage into a substantially constantunidirectional voltage.

This voltage is applied as a polarizing potential to the outputelectrode of thefirst stage. For this purpose a, conductive coupling isprovided between the integrating network and the output electrode ofthefirstamplifier stage. i

There are developed, in. the coupling, voltag varyinsinresponse tocurrent changes in the output circuit of the first stage. These-currentchanges result from the impedance variation of the electronic deviceunder the. control of the impulses applied to the input circuit thereof.These developed voltages are applied to the input circuit of thesucceeding stage to efiect a control thereof, whereby amplified impulsesare produced in the output circuit of this stage. A portion of theenergy of theamplified impulses is used to maintain the voltagedeveloped ,by the integrating circuit and the remainder may be used fora control purpose.

The connection between the conductive cou--.

cathode potential normally is sufiiciently negative to' effect cut-offof anode current. The currents representing the impulses in the ouputcircuit of the first stage effect the development in the coupling ofvoltages which, when applied to the input.

circuit of the succeeding stage, render the electronic devicethereofconducting. Thus, if a composite television signal including videosignals and put circuit of the first stage, the electronic device of thesucceeding stage is rendered unresponsive to jsignals having therelatively small voltage amplitudes of the ,video signals. It is onlywhen the signal amplitude increases to represent a synchronizingimpulsethat the electronic device of the second stage responds to amplify suchasignal. I Thus, the devicein accordance with themstant invention notonly operates as a more efi'icient amplifier but also may serve as a,means for separating the synchronizing impulses from the video signalsin a television syste For a. better-understanding of the inventiontogether with other and further objects thereof, reference is had t thefollowing description taken in connection with the accompanying drawing,and its scope will be pointed out in the appende claims.

In the accompanyingdrawing, the single figure is a circuit diagram of anamplifier embodyin the instant invention in what at present is considered a preferred form. Referring now more particularly to thedrawing, there is shown a source of impulses I. This source may be agenerator of periodic impulses.

of the tube is shunted by a grid leak resistor 4. The screen grid of thetube 3 is connected through a resistor 5 to a source offpositive directcurrent Voltage, such as a battery 6, and is bypassed to ground througha condenser 1. The

suppressor grid. of the tube is connected directly to ground so that itis maintained at the cathodepotential. The anode of the tube 3 isconnected to a source of positive'potential which will be described morefully hereinafter.

The second stage of the amplifier includes an output or driven vacuumtube 8, the anode of which is connected directly to the positive ter-'minal of the battery 8. The screen grid of the tube 8 is connectedthrough a resistor 9 to the battery 6 and is also bypassed to thecathode through a condenser II]. There is-also provided a resistor IIfor establishing a desired potential on the screen grid of vacuum tube8. The cathode of the tube 8 is connected to a load impedance whichincludes a resistor 12 and an integrating or energy storage network I3.The integrating network comprises the parallel arrangement of a resistorHi and a condenser l5 and is connected between the resistor l2 andground. The cathode of the tube 8 is also connected through a couplingresistor Hi to the anode of the tube 3. The coupling resistor alsoserves as the load for the output circuit of the tube 3. The controlgridofthe tube 8 is connected to the anode end of the coupling resistor [6.j r

The output circuit for the amplified impulses is derived from theterminals of the load impedance of the tube 8. This circuit is coupledby a condenser I! to the apparatus l8 which is. to be controlled by theimpulses.

Referring now to the operation of the system, assume that there isapplied to the input circuit of the tube 3 a series of unidirectionalimpulses of such polarity that the grid-to-cathode potential of thistube is decreased thereby. As a result of the repetition of theseimpulses in the output circuit of the tube 8 impulsive energy is appliedto'the integrating network I3. The time constant of. thiscircuit is suchthat there is maintained at the terminals thereof a substantiallyconstant unidirectional voltage. This voltage maintains the cathode ofthe tube 8 at a relatively high decreases The resultant decrease of thevoltage .drop across the coupling resistor I8 is siiflicient to raisethe grid-to-cathode potential of the tube 8 to the point where this tubebecomes conducting. Thus, it is seen that there is repeated in theoutput circuit of the tube 8 the signal hich exists in the input circuitof the tube a. Each of the amplified impulses repeated in the outputcircuitof the tube 8 produces sufficient appliedtothe input circuit ofthe tube 3, are of first stage of the amplifier. The input circuitinsufilcient amplitude to cause the anode current in this tube toapproach cutoff, thus tube 8 remains biased to or beyond cutoff and novariations in the output current of tube 8 occur. Video signals,therefore, are not repeated into the out-. put circuit of the secondamplifier stage; However, the.amplitude.0f the synchronizing signals issuflicient to reduce the anode current of the tube 3tothe point wherethe tube 8 becomes conducting. The synchronizing signals then arerepeated in the output circuit of the second amplifier stage.Consequently, it is seen that the apparatusin accordance with thepresent invention will function as a separator of the synchronizingsignals from'the video signals in a television system.

While it will be understood that the circuit specifications of theamplifier may vary according to the design for any particularapplication, the following circuit specifications for an amplifieremployed for either of the applications described are included by way ofexample only:

The amplifier in accordance with the instant invention has a number ofdesirable and advantageous features. The output voltage supply for thefirst amplifier stage which is taken-from energy stored in the outputcircuit of the second stage results in a substantial increase in theoverall efliciency of the amplifier from the standpoint of powerconsumption. The derivation of. the

acteristic of the amplifleris its capability of producing a relativelylarge output.

While there has been described what, at present, is considered thepreferred embodiment of the invention, it will be obvious to thoseskilled in the art that various changes and modifications may be madetherein without departing from the invention, and therefore, it is aimedin the appendedclaims to cover all such changes and modifications asfall within. the true spirit and scope of the'invention.

What is claimed is: 1. In an electronic amplifier, a first stage havingiiiput and output circuits, a second stage having input and outputcircuits, an energy storage circuit including an integrating network'connected in the output circuit, of said second stage, means forenergizing the output circuit of said first stage from said storagecircuit, and means for deriving from said energizing vmeans a.contr0l,put 'circuitoi. said second stage.

voltage for the input circuit of said second stage,

whereby to reproduce in the output circuit of said I second stagesignals impressed upon the input,

circuit of said first stage. g

2. In an'electronic amplifier, an output electronic device having inputand output circuits,

, trol voltages upon said input circuit of said output electronicdevice, whereby said signals' are reproduced in the output circuit ofsaid output electronicdevice to energize said storage network.

3. In a two-stage amplifier, a coupling arrangethe output circuitof thesecond' stage including an integrating circuit, means for deriving fromsaid integrating circuit a substantially constant cuit of the firststage, andmeans for deriving from said coupling means a control voltagefor the in- .4. An impulse amplifier comprising, an input vacuumtubehavirig a control grid. and an anode, I means for impressing impulsevoltage upon said grid to produce related impulse voltages at saidanode, an output vacuum tube having a control grid and a cathode, a-loadimpedance including an integrating network, means including said networkfor maintaining said cathode at a substan-' ance with variations of theanode voltage 017 said input tube in a manner to eifect the repetitionby said output tube of impulses to said network.

5. 'Apparatus for amplifying signal impulses v comprising, adrivingvacuum tube having input and output circuits, said output circuitincluding an anode, a driven vacuum tube having input and outputcircuits, said input circuit including a cathode and a control" grid, aload impedance for the output circuit of said driven tube including anintegrating network connected to said cathode, a load impedance for theoutput circuit of said driving tube including a resistor connected Iment between the stages comprising a load for r-unidirectional voltage,means for coupling said v unidirectional voltage to supply the outputcirbetween saidcathode and said anode, means for coupling said grid tosaid anode, means for impressing voltage impulses of negative polarityupon the input circuit. of said driving tube, whereby to produceamplified voltage impulses of positive polarity in the output circuit ofsaid driven tube, said integrating network utilizing said positiveimpulses to produce a substantially constant supply voltage for theoutput circuit of said driving tube.-

6. Apparatus for separating synchronizing impulses from a compositetelevision signal including video signals and synchronizing impulsescomprising, a vacuum tube having input and output circuits and arrangedto reproduce in said output circuit a composite television signalimpressed upon'said input circuit, a second vacuum tube having input andoutput circuits, said second tube output circuit including a series'arrangement of a source of unidirectional energy and an energy storagenetwork, an impedance element connected to the input circuit of saidsecond tube, said impedance element also serving to couple said energystorage circuit to the output circuit tially constant unidirectionalpotential, means including a conductive coupling to impress saidunidirectionalpotential upon the anode of said in put tube-and means forderiving from said coupling-a control voltage for the grid of saidoutputtube, said control voltage varying inaccordof "said first tube,wherebysaid reproduced composite television signal developscorresponding voltages-in said impedance element, and means includingsaid impedance element for biasing the input circuit of. said secondtube so as to render the output circuit thereof responsive only to thedeveloped voltage representing the synchronizing impulses.

